Insulator and method of producing conducting coating thereon



April 1942- s. L. SANTOMIERI 2,281,173

INSULATOR AND METHOD OF PRODUCING CONDUCTING COATING THEREON Filed Jan.10, 1940 IN VENT OR. ,SsZasZzkvz/Z- flflzZ-omz'erv wa ATTORNEY.

Patented Apr. 28, 1942 msuu'ron AND METHOD or rnonucmo counoc'rmocos'rmc mason Sebastian L. Santomierl, Columbus, Ohio, as-

signor to Victor Insulators, lne., Victor, N. Y., a corporation of NewYork Application January 10, 1940, Serial No. 813,211

11 Claims.

This invention relates to an insulator having a dielectric ceramic bodyand a resistant coating that is partially conducting, withmoreparticular reference to high tension insulators, the surfaces of whichare sometimes partially coated with a conducting glaze to maketheinsulator' free from noise and radio interference by eliminatingsurface leakage or corona, and it has for its object to afford a coatingor glaze that can easily be controlled and applied, which is economicalto produce and suillciently conductive to dampen out corona and overcomeradio interference, and which is permanently bonded or attached to thebody of the insulator so that it is not subject to oxidation, chippingor wear, but is as permanent and enduring as the porcelain insulatorbody it- "If;

It has heretofore been proposed to coat insulators with conductingmaterials, but such coatings have either been costly to apply or of suchcharacter that they quickly wear off or lose their conducting emciency,and it is a particular purpose of the invention to afford a coating orglaze that can be manufactured and applied cheaply and which becomes anintegral part of the insulator body, so as to be chemical resisting andcompletely unaffected by weather or by the usual wear to which aninsulator is subjected.

One purpose of the invention is to utilize coating materials that arecomparatively inexpensive and can be readily applied to an insulatorbody without increasing its cost of production over previous methods, soas to afford a glaze of stable character that is not soluble oraiiectedby any acids and will maintain its conductive efiiciency indefinitely.

Another object of the invention is to afford a coating material that isapplicable to insulators formed of porcelain or other silica-containingmaterials, and which during the firing process becomes a permanent andintegral part of the body of the insulator by a chemical action, butwithout in any way affecting or lessening the nonconductivity of thebody of the insulator, while providing a glaze that is suflicientlyconductive to prevent energy losses and radio interference.

It has heretofore been proposed to coat porcelain insulators with ametallic glaze, or with a mixture of metallic and silicate glazes, butthese all have the objection that the final or resulting coating is athin glaze metallic in form and containing free metal, since the metalsthat have been so proposed are resistant to kiln firing conditions, andthe resulting glaze is therefore sub- Ject to abrasion and chemicalaction which will 55 shorten its life, and it is a particular purpose ofthis invention to provide a partially conducting glaze or coating thatis not of a metallic char-' acter and which contains no free metal, suchmetal as is introduced into the coating composition in the beginningbeing united chemically during the kiln firing treatment with the othermaterials in the coating composition and with the body of the insulator,and thus becoming an integral and permanent part of the insulator bodyso as to resist any action or wear to the same extent as a ceramicinsulating material.

It has also been proposed to coat insulators with glazes containingmetallic oxides and to apply a reducing agent after firing to make thecoating conductive, but this is a slow and expensive procedure,resulting in only a surface coating in the nature of a thin metal filmwhich will oxidize and wear away in time, before the insulator body haslost its useful life, and it is a particular purpose of the invention toprovide a glaze or coating that will have the required conductivecharacteristic and which at the same time is so united to the ceramicbody as an integral part thereof as to wear and function efliciently aslong as the insulator body, so that the life of the latter is notreduced by the coating or glaze wearing, chipping, or in any way losingthe e!!!- ciency it possesses in the beginning.

so To these and other ends. the invention consists in the constructionand procedure that will appear clearly from the following descriptionwhen read in conjunction with the accompanying drawing, the novelfeatures being pointed out in the claims following the specification.

The drawing illustrates a sectional view of a conventional type ofinsulator made by molding and thereafter firing a body ofsilica-containing material such as clay, feldspar and fiint, andillustrating applied to a portion of its surface thereof a coating inaccordance with the invention. This is a continuation in part ofapplication filed January 19, 1939, Serial No. 251,777, and theinvention is equally applicable to insulators made from anysilica-containing ceramic material, as well known in the art.

I have ascertained that a successful and practical coating, that issufiiciently resistant and conductive for the purpose, can be obtainedby using a composition including as one of its materials lime, orcalcium carbonate, commercially known as whiting, or any salt ofcalcium, or other of the materials in its group, that is unstable andwill break down in firing, together with magnesia, and iron or steelfilings, or iron Imetals including iron,

0! the I ceramic body attached thin metallic film hydroxide, or othermaterial from the-group of that is unstable and will break down infiring, preferably mixed with a sumcient amount by aluminum silicate inthe form of clay, which makes the mixture easy to apply to the surfaceby brushing or spraying thereon, previouslyto the firing operation.

The coating composition may be applied to either a glazed or unglazedsurface of an insulator, and various materials may be used to obtain thedesired result.

Mendeleefs' Periodic Table, namely magnesium, calcium, zinc, strontium,cadmium and barium, may be used, either in sulfate, sulfide, fluoride,or any unstable salt.

In place of iron, I have'successfully used cobait, or nickel, inunstable form, and may use an unstable compound derived from anymaterial in the section from group VIII of Mendeleefs Periodic Table whih contains iron, cobalt, and nickel.

Successful results are obtainable by combining an unstable salt of anymaterial in group II, in the form of a carbonate, sulfam, sulfide,fluoride, or otherwise, with an unstable compound derived from anymaterial from the section of group VIII which contains iron, cobalt, andnickel. Where the expression "unstable is used throughout thespecification and claims, I intend by this to define a material thatisunstable when subjected to heat and breaks down or decomposes durin thesubsequent firing of the insulator body.

It has been found thata coating produced with iron, calcium carbonate,and clay, possesses a high coeflicient of expansion, and in order tolimit such expansion, a small amount of zirconium oxide can be added to.the mixture.

As an example, one composition of materials that has been found. toproduce a satisfactory and eflicient coating contained the following:

Per cent Iron hydroxide 64.4 Calcium carbonate 23.5 Clay 6.7 Zirconiumoxide 5.4

Other compositions have been usedsuccessfully containingthe variousalternative materials hereinabove referred to, in place of ironandcalcium. After the molded ceramic body is coated with a compositionsuch as described, it is fired in an oxidizing atmosphere, subject totemperatures of from approximately .2000 F. to 2500" F., such as areusually employedin the production of in sulators of this generalcharacter. I

While it can not be stated with certainty what reaction takes placeduring firing, it is believed that the iron, cobalt, or nickel mostlikely ceases to function as. a-metal after firing, having become alongwith the silicon, basic in reaction, and mating with the calcium orother material of its group. The result probably is to produce a,

calcium ferro-silicate, the ferro-silicate taking the place of thecarbonate on firing, resulting in a conducting non-metallic glaze thatis firmly and permanently bonded to the outer body portion of theinsulator and becomes an integral part thereof as distinguished from amechanically or covering The method and composition may be otherwisemodified without departing from the essentials of the invention, andthis application is'intended to cover any adaptations or changes, eitherin 75 iron,

of water and held in suspension the section of group The magnesia may bep omitted, and any material from group II of the form of a carbonate,

-. contains iron,

* the presence of heat; and a clay,

the composition or the procedure in applying it, that come within thepurposes of the invention or the scope of the following claims.

I claim:

1. A high tension electric porcelain insulator having a fired surfaceconducting coating consisting of a material derived by firing a coatedcomposition containing an inorganicrcoi npound of an element of group IIof the (periodic table and an inorganic compound of an element from VIIIof the periodic table which contains iron, cobalt, and nickel.

2. A high tension electric porcelain insulator having a fired surfaceconducting coating consisting of a material derived by firing a coatedcomposition containing an inorganic compound of, an element of group IIof the periodic table, an inorganic'compound of an element from thesection of group VIIIof the periodic table which, cobalt, and nickel;and silicon. 3. A high tension electric porcelain insulator having afired surface conducting coating consisting of a material derived byfiring a coated composition containing inorganic compounds of calciumand iron. I

4. A high tension electricporcelain insulator having a fired surfaceconducting coating consisting of a material derived by firing a coatedcomposition containing inorganic compounds of calcium, iron, andsilicon.

5. The method of producinga high tension."

usual ceramic insulator firing temperature.

6. The method of producing a high tension electric porcelain insulatorwith a conductin surface which consists in coating the surface of asilica-containing ceramic body with a composition containing aninorganic compound of anelement of group II of the periodic table thatis unstable in the presence of heat, and an inorganic compound of anelement from the section of group VIII of the periodic table whichcontains iron, cobalt, and nickel, said compound being unstable in thepresence of heat, and thereafter subjecting the insulator body andcoating to a usual ceramic insulator firingtemperature.

7. The 'method of producing a high tension electric porcelain insulatorwitha conducting surface which consists in coating the surface of asilica-containing ceramic body with a compositioncontaining an inorganiccompound .of an element of group II of the periodic table which isunstable in the presence of heat, and an inorganic compound of anelement from the section of group VIII which contains. iron, cobalt, andnickel, said compound being unstable in and thereafter subjecting the,insulator body and coating to a usual ceramic insulator firingtemperature.v

'8. Theymethod of producing a high tension electric porcelain insulatorwith a conducting surface which consists in'coating the surface of asilica-containing ceramic body with a composition containing aninorganic compound of an element of group II of the periodic table, andand thereafter subjecting the insulator body and coating to a usualceramic insulator firing temperature.

9. The method of producing a high tension electric porcelain insulatorwith a conducting surface which consists in coating the surface of asilica-containing ceramic body with a composition containing aninorganic compound of calcium and iron hydroxide. and thereaftersubjecting the insulator body and coating to a usual ceramic insulatorfiring temperature.

10. The method of producing a high tension electric porcelain insulatorwith a conducting surface which consists in coating the surface of asilica-containing ceramic body with a composition containing aninorganic compound of an element of group II of the periodic table, ironhydroxide, and a clay, and thereafter subjecting the insulator body andcoating to a usual ceramic insulator firing temperature.

11. The method of producing a high tension electric porcelain insulatorwith a conducting surface which consists in coating the surface of asilica-containing ceramic bodywith a composition containing an inorganiccompound of iron which is unstable in the presence of heat, and aninorganic compound of an element of group II of the periodic table whichis ustable in the presence of heat, and thereafter subjecting theinsulator body and coating to a usual ceramic insulator firingtemperature.

SEBASTIAN L. SANTOMIERI.

